Plagiarism can be looked at two ways, as a legal matter (copyright infringement) or an
ethical matter (borrowing too heavily from an unattributed source, even if it doesn't
break the law).

Copyright Infringement

While I'm not a lawyer, I can tell you the understanding that I have: Unless it can be
shown that a work uses about a third of the written language of the source, or closely
paraphrases it for many long passages, there is nothing actionable under the law. Ideas
can't be copyrighted, nor can titles (titles can only be trademarked, and then only if
you're using them for merchandising, and even then only if it's not a common word).

Unethical Copying

This is what most people mean when they say "plagiarism." If you write a manuscript
that, point for point, follows an unattributed source, and you try to pass it off as original
work, you have probably crossed the line into unethical copying. The punishment is not
legal prosecution (though in the film business you can sue for a portion or even the
entirety of earnings, if the copy gets filmed and the original therefore can't), but rather
the scorn of the publishing industry. In several famous cases, the punishment for this
kind of copying was public exposure, public humiliation, and in the case of novice
writers, the end of all hope of getting published (at least under the name you were
using!). Publishers have long memories when it comes to such offenses.

Working with Sources

Copyright infringement and unethical copying are not only rare, it is almost impossible
to inadvertently commit such an offense (the lame defense of a certain romance writer to
the contrary notwithstanding). There are many different kinds of sources, and many
ways one work can resemble another. So let's consider some of the possible sources of
stories, and see what the rules are.

Just the facts.

You can't copyright facts. You can only copyright the language used to
recount those facts. (That's why mapmakers and phone directory publishers insert false
data - in order to prove that catch someone else copying instead of doing their own
original research.) And when you base a story on a factual source, like history, you can
change it any way you want - legally, that is. Ethically, I think you need to take some
care for the sake of your readers and for the sake of the reputations of other people -
even the dead. When your story is at a far remove from the original facts, then you can
do what you want. If you base a character on a real person, as I did in basing some of
Alvin's life on incidents from the life of Joseph Smith, or even base a story point for
point on a historical source, as I did in basing the plot of the Homecoming series on the
first portion of the Book of Mormon, as long as you make drastic changes you are
perfectly safe - drastic enough changes make it so the reader does not expect to be getting
the facts straight.

Still, I feel a sense of responsibility toward the facts. For instance, because I believe the
Book of Mormon to be what it purports to be - a modern translation of a genuine
ancient document, created under divine direction - I felt a great responsibility in
adapting it to a new setting, even though I knew few readers would get the connection.
Therefore I bound myself strictly by the moral stance of the original - the good guys
remain good, the bad guys remain bad, and whenever the original source ascribed a
motive to someone for their actions, I stuck to the motive given by the book. Likewise,even though I depart widely from Joseph Smith's life in the Alvin Maker stories, I
nevertheless try to remain true to his personality and character as I have come to
understand him through research - I don't ever have Alvin do anything that is more
morally questionable than things Joseph Smith actually did, and insofar as possible, I
make his motives gibe with Joseph Smith's motives.

There are writers who feel no such compunction, of course. Practically everyone who
does a story about the life of Jesus these days seems to feel obliged to make Judas the
misunderstood hero, for instance. I think that's juvenile and cheap, but that's a review,
not an ethical charge. Oliver Stone crossed the line much farther, I think, with his film
JFK. Better researchers than I have eviscerated his mistreatment of history, so let me
merely say that as I understand it, Stone took enormous liberties with the story he was
telling and especially with some of the real people he portrayed. For instance, one man
who denied to his deathbed that he had anything to do with or knew anything about any
plot to assassinate Kennedy, Stone shows confessing. This is a lie, right? Stone knew the
man never confessed, and yet he showed him confessing. Now, if Stone had distanced his
material from the source story as I did with Homecoming or the Alvin Maker stories, he
could do that with impunity (though I don't). However, in JFK he left everyone in their
original setting, and he haunted every talk show spouting off about how he was finally
getting the truth out where the American people could see it. Later, when he was called
on his misdeeds, he whined that it was "just a movie" and "fiction." In a country that
keeps Clinton as president, I guess he can have it both ways. Everybody has to draw the
line where they feel right about it.

Slander and Libel.

When you're dealing with real people, of course, another issue comes
up that is quite different from plagiarism. Slander and libel both consist of false and
damaging statements about a person (slander is spoken, libel is printed). In court, there
are additional tests - if a person is famous, in order to prove he was libeled or slandered
he has to prove that the person who lied about him did so with malicious intent or with
reckless disregard for whether the charges were true or not. This standard is hard to
prove, since it goes to motive. (In other countries, no such standard has to be met - even
famous people have a right to insist that people not lie about them.)

There are certain protections for a writer dealing with real people. First, you can't libel
the dead. That is, once a person has died, no one has standing to sue on their behalf, and
that's why Stone could get away with lying about that one dead guy. Second,
truthfulness is a complete defense - if you can prove that your charges are true, there is
no libel. Third, you can hide behind your sources - if you rely on a seemingly reputable
source that turns out to be inaccurate, chances are you'll get away with a retraction, an
apology, and a correction. Fourth, if you disguise the details about the person so
thoroughly that most people would not know whom the character was based on, and the
only thing that made the person identifiable was that he sued you, he'll be hard-pressed
to show how your story, as it stood, damaged him.

But the best way to avoid such problems is obvious: Don't base your fictional characters
on living persons. In those rare cases when you must openly base your story on a real
incident or person, get permission in writing and, if possible, involve them in the
process. Thank them graciously in your acknowledgments, and make an honest effort to
be fair. But then, if you're doing that, why make it fictional?

Necessary Resemblance.

When you are going to original sources that are not factual,
chances are very good that you're going to come up with elements in your story that
resemble elements in stories by other people who went to the same sources. What could
be more obvious and innocent? For instance, in the Alvin Maker series, I arranged for
some research into American folk beliefs and practices, and used them in my fiction. But
anyone else who wanted to use American folk beliefs (or European folk beliefs that were
the source, in turn, of American folk beliefs) might very well come across the same
elements I used. There is no problem at all with incorporating such elements into your
work. The resemblance is unavoidable, and it harms neither party.

Sometimes, though, another work of fiction is your source. For instance, when writing
a parody (like Pat Murphy's recent sci-fi retelling of The Hobbit), you can freely follow
the storyline of the original - as long as it's clear that parody is your purpose. Sometimes
you can be too faithful to the original - a flaw I think Murphy's novel suffers from - but
the result is not charges of plagiarism, but merely disappointment and bad reviews. But
no one watching Mel Brooks's Spaceballs would dream of charging him with plagiarism
or unethical copying - though few would charge him with being very funny, either ...

Derivative?

What if, however, your "research" consists of reading another work of
fiction and then "thinking up your own." I'll confess that when I first picked up Sword
of Shannara, eons ago, I quickly decided that Brooks's only source was Lord of the Rings,
and I put it back down. But this was not a charge that Brooks plagiarized or copied
unethically. Rather I simply detected way too much influence, and not enough original
vision for my tastes. That is, Brooks did nothing unethical. He simply did something
that I found artistically displeasing. Millions of readers disagree with me, and I confess
that since that time I've seen many works published that have far less original content
than Sword of Shannara did, so I daresay my original judgment was unfair. Still, when
you work within a genre utterly dominated - arguably created - by one towering writer,
you're going to run the risk of being called "derivative."

However, keep in mind that as far as we know, Shakespeare almost never wrote a story
"from scratch." His sources were usually historical, and often were stories that had been
depicted in plays by other playwrights. Originality was much less a concern in that era -
indeed, it was regarded as a plus if you could point to an admired source for your work.

And you also have to be aware of the fact that your audience's sophistication will affect
the way they receive such resemblances. If the only science fiction novel you have read is
Starship Troopers and then you read Ender's Game, you're going to go ape over the fact
that there are insectoid aliens, etc. Card is a thief! But then when you realize (1) Card
has never read Starship Troopers and (2) there was a long history of sci-fi stories about
combat with insectoid aliens that both Heinlein and Card borrowed from, you relax a
little. We weren't being "derivative," we were "working within a tradition."

The Anxiety of Influence

Influence happens. It's unavoidable. Indeed, many an English teacher acts as if the only
reason to study literature is to detect influences.

The problem is that real influence is (or should be) unconscious. That is, because you
have read certain writers whose stories have been thoroughly absorbed into your
memory, you will unconsciously borrow motifs and ideas from those pivotal works
without even realizing you're doing it. (For instance, my story "Unaccompanied Sonata"
spewed out fully formed; only later - years later - did I realize how much my story owed
to Lloyd Biggle Jr.'s "Tunesmith," which I read when I was eight or nine years old and
had long since forgotten.)

Some novice writers, having absorbed utterly wrong lessons about what makes good
writing, try to be "influenced" by writers they admire. This is not influence, however - it
is borrowing. And it's legitimate, though it is customary to acknowledge your conscious
borrowings - the way I acknowledged my debt to Ursula K. LeGuin by using her word,
ansible, for the instantaneous communication device in the Ender books. I didn't have
to do that, however - I only did it because I was so naive when writing "Ender's Game"
(the original novelet) that I did not realize that instantaneous communication in a
universe with lightspeed travel was a common motif. As far as I knew, I was getting it
from her, so I tipped my hat to her. In no other respect, however, does Ender's Game
resemble any of the Hainish novels.

Many writers, however, far from borrowing or seeking to be "influenced," are
desperately afraid of inadvertent influence to the point of paranoia. Since every good
idea has already been used, getting too anxious about such chance resemblances is a waste
of time.

Here's my rule: Any idea you really like that absolutely works for your story is your
idea, no matter who else might have used it before. The only limitation on this is what
the audience will stand for - if you end your novel with the hero standing before a fire
and the only way the ring gets thrown in is because someone else bites off his finger and
then falls in, well, your audience is likely to be a bit disgusted - the resemblance is too
close, the source way too well-known. Only if your intent is humorous can you get away
with it.

You should not be penalized for having read widely, however. If your story has
elements that you recognize as being similar to a book by someone else, so what? As
long as it's your own story, and those motifs feel important and true within the context
of your work, they're your ideas now. If you think the resemblance is close enough and
the other work well known enough that you want to acknowledge the resemblance, go
ahead - it costs nothing to add a line to your Acknowledgments section, or even to slip a
sly acknowledgment into the text of the story. (I tipped my hat to Tolkien for the debt
that all fantasists owe to him by having a character - was it Alvin? - dream a dream that
was obviously a scene from Lord of the Rings. I meant it as a joke between me and my
readers, but some have unfortunately sought to reconcile the two works as if I were
asserting that they take place in the same fictional universe. I was not.)

Does Crais owe Parker a royalty for having a violent sidekick to come in and do his
hero's dirty work? Not at all. It's an extremely useful device, and Crais has made the
characters real and definitely his own. And will someone who has a character involved
in midwifery who foretells the future of the babies who are born owe anything to me
because I have such a character in the Alvin Maker series? Not at all. I'd be flattered to
death to think that my work might actually influence somebody else. And I appreciate
the care that this writer has taken to make sure no lines have been crossed. Sounds to
me like you've followed all the rules. So finish the book and publish it!